The present invention relates to a metal laminate type cylinder head gasket for an internal combustion engine with an auxiliary combustion chamber.
In an engine with an auxiliary combustion chamber, a cylinder head is provided with a mouth plate to close the auxiliary combustion chamber. When the engine is operated, gas at first combusts at the auxiliary combustion chamber, and then gas at a cylinder bore combusts. Therefore, the mouth plate receives combustion pressures from both the auxiliary combustion chamber and the cylinder bore.
As shown in FIGS. 1 and 2, a cylinder head H is provided with a depression K, to which a mouth plate L is inserted, so that an auxiliary combustion chamber M is defined inside the depression K. A gasket 10 is installed between the cylinder head H and a cylinder block J to seal therebetween. The mouth plate L is supported partly by a portion N of the gasket 10.
As stated above, when the engine is operated, combustion pressure is applied to the mouth plate L, so that large pressure is applied to the portion N of the gasket. Sometimes, the mouth plate L moves up and down.
In the conventional steel laminate gasket 10 as shown in FIGS. 1 and 2, the gasket 10 is formed of an upper plate, lower plate and three middle plates. A wire ring is installed around the cylinder bore Hc. Since the gasket 10 does not resiliently support the mouth plate, combustion gas is liable to leak through the mouth plate.
In order to resiliently support the mouth plate, one of the middle plates may be replaced by a plate with beads at the portion N of the gasket, which is disclosed in Japanese Patent Publication (KOKAI) No. 59-90745. Also, a bead may be formed on a plate at a portion outside the mouth plate to seal therearound (Japanese Patent Publication No. 60-162037). Further, in case a bead outside the mouth plate intersects a bead around the cylinder bore, additional beads may be formed outside the intersecting portions of the two beads (Japanese Utility Model Publication No. 63-166651).
In U.S. Pat. Nos. 4,791,897, 4,803,965 and No. 4,809,653, one of the middle plates is provided with different kind of beads on and around the portion N under the mouth plate L to support the mouth plate L and seal therearound.
The gaskets as proposed by the patents operate as intended. However, in case the gasket can not be strongly compressed or rigidity of the cylinder head is not so strong, the above gaskets are not suitable. Namely, sufficient tightening pressure can not be applied to a portion where high tightening pressure is required, i.e. intersecting portions of the bead outside the mouth plate and the bead around the cylinder bore. Therefore, combustion gas may leak from the mouth plate or the cylinder bore.
Accordingly, one object of the invention is to provide a metal laminate type cylinder head gasket, which can securely seal around a mouth plate and a cylinder bore.
Another object of the invention is to provide a metal laminate type cylinder head gasket as stated above, which is useful for an engine where the gasket can not be sufficiently compressed.
A further object of the invention is to provide a metal laminate type cylinder head gasket as stated above, which can be easily and economically manufactured.
Further objects and advantages of the invention will be apparent from the following description of the invention.